I think th eOP shoulda added in another option:
all the above.
I sleep on my left, right, face down face up. Always on the right though because I'm right handed. Used to be so I could reach for my glasses right away.
I like to spoon for a bit then turn over and fall asleep.
The last person I slept with used to knee me, kick me and elbow me. She used to open the bedroom window (in the middle of winter) and then crank up the electric blanket (then wondered why her utility bills were so high).
The final straw came one night when I was fast asleep adn she unceremoniously started yanking on one of my pillows. In my stupor I grabbed onto it and she actually grabbed it with both hands, put her knees to my back and yanked it away from me, leavin gme with one pillow about as thick as a towel. I law there for a minute and thought, enough of this bullshit and took it back. She said "really, you don't get ALL the pillows" I said "I've got one, you've got 5" she looked around and she'd knocked her 4 onto the floor.
I law there for a minute or two and said to myself "fuck this" and got up and left (at 3:30 am)
She called the next morning and said "why'd you leave"?
I said "because sleeping is NOT a full contact sport and shouldn't require body armor".......